my charger puts in 4.23V not 5V, putting 5V in will eventually damage the battery and possible make it vent with or without fire = literally toast N900 A LiPo battery should be charged with between 4.15 - 4.23V. I only use the 2mm plug system, it is not connected to a normal nokia charger, but it is connected to a LiPo charger, and depending on the mood i have 6 different chargers to choose from, all battery test are of course done with 1 only